Now I found a blog post on Pigs, Gourds & Wikis which explains the error is because iBooks doesn't allow spaces in file names.

So I opened the toc.ncx file in Notepad +. I change all the file names, like the one listed above, so all the blank spaces I changed to underscores_ .
However when I tried to reupload the file I'm still getting errors. I thought I'd finished but I haven't. Please, any ideas how I can fix this?